Altair astro 183M, PixInsight, Starburst again - how to remove

[txo]

Hello,

I was unable to find a solution even though went through relevant posts so trying again. Have actually anybody who was asking this question been able to get rid of the damn starburst?

I integrated master dark using this http://pixinsight.com/tutorials/master-frames/index.html , my exposure time (240s), gain (200), temperature (-10C) were always the same, 40 dark subs. In order to isolate the problem I did not use bias nor flats. I tried all the combinations in ImageCalibration settings. Turning off calibration and optimization only reduced the flare, didn't remove it however. I even tried non integrated flat sub with the same result. Only significant difference was final noise. The only solution I was able to find was don't use PixInsight..

thank you

This is basically the same problem is this one> https://pixinsight.com/forum/index.php?topic=13266.0

If anybody from pixinsight team wanted to have a look at this I could provide all the data.

[STEVE333]

From your explanation this sounds like it might be a data problem not a PI problem. I'm not defending PI. Just trying to understand your problem.

If this is a real cmos starburst problem, then, I would expect it to be present no matter which image processing program you are using.

Are you saying that you have processed the same data with another image processing program (not PI) and the starburst is not present? If that is the case, then, I can understand your frustration with PI. Which image processing program did you use that successfully removed the starburst?

Steve

[Juan Conejero]

I'll quote myself from the other thread:

As always: We cannot help without a sample of the data where problems can be reproduced, analyzed and described. Sorry, we don't have crystal balls. So if you want to help us solve an issue related to specific data, or possibly a bug (damn, I am not perfect, sorry), then we need the specific data. Or a crystal ball, at your option.

Let's try the first option first. Can you upload a complete and sufficient data set where this problem can be reproduced consistently (dropbox, etc)? Thank you so much in advance.

[ngc1535]

Hi,

I am super confused by this thread (and the archived one). Is this simply a specular reflection from a bright star due to a shiny surface at the edge of the chip?
This is a very common malady. Unfortunately there isn't really an easy or good fix for this in terms of processing. If this is the issue, it is an acquisition problem. Rotating the camera slightly can sometimes help. I have lots of examples of this issue... isn't it the same as this?



I have some other pictures that very closely match the type the OP shows.
-adam

[sharkmelley]

Hi,

I am super confused by this thread (and the archived one). Is this simply a specular reflection from a bright star due to a shiny surface at the edge of the chip?

The star burst pattern is a feature of the sensor and is obvious in the darks as well as the lights.

Good examples are in this Cloudy Nights thread.
https://www.cloudynights.com/topic/599475-sony-imx183-mono-test-thread-asi-qhy-etc/?p=8239029

The OP needs to provide some example raw files otherwise it's not clear why calibration is apparently not working.

Mark

[ngc1535]

Wow! OK that is super weird.
Thanks for pointing out this example
That is definitely a camera thing.
-adam

[txo]

I'm doing some more investagtion to this. I'll come back soon.

[chris.bailey]

Wow! OK that is super weird.

And what is even weirder is that the exact starburst pattern varies every time the camera is powered up so darks not only have to be taken with the exact same duration, time and gain but also each time the camera is powered up. Sold mine, back to CCD!

[txo]

I retook darks and managed to get rid of the starburst. It certainly wasn't during the same camera uptime as lights. Now I'll try to take wrong darks.

There are only two things I did diferently now. I took them during night time and used usb3 instead of usb2. So originally maybe some light managed to get through or there is some weird usb3 vs. usb2 issue. Or it's completely random. We'll see.

[wvanreeven]

USB3 allows for much faster downloads than USB2 with USB2 leading to amp glow in some camera models. I am not sure if this one is subject to that as well but it could be the cause. In any case, always try to shoot lights and darks using the same port.

Of course I could be wrong and this has nothing to do with the starburst.


Wouter

[pfile]

it may or may not - it depends on whether or not this particular sensor or camera downloads the image into RAM before it sends it to the USB interface.

if the imager or camera has some kind of ram buffer the cmos readout speed is probably the same regardless of usb2/usb3.

rob

[sharkmelley]

USB3 allows for much faster downloads than USB2 with USB2 leading to amp glow in some camera models. I am not sure if this one is subject to that as well but it could be the cause. In any case, always try to shoot lights and darks using the same port.

Of course I could be wrong and this has nothing to do with the starburst.


Wouter

It appears that there could be a difference between USB2 and USB3. ZWO mentions the difference between UBS2 and USB3 here:
https://astronomy-imaging-camera.com/tutorials/what-is-amp-glow.html

Mark

[wvanreeven]

Thanks Mark for posting that link. I predominantly use ZWO cameras and wrote my comment from that experience. Not sure if that applies to cameras of other brands as well.


Wouter

[txo]

OK, guys. I havan't managed to reproduce the problem and now my calibration is fine no matter what. Moral of this story seems to be, if you're confronted with poor calibration just retake your calibration subs.

[Juan Conejero]

Glad to know it's working.

So... PixInsight is working correctly calibration wise, and you don't have to use other applications to work with these files necessarily. There is no bug here, so case closed.

Just a reflection. A note about these conclusions, especially on other public forums, when and where appropriate, would be nice. Spreading the voice that PixInsight—or for that matter any application—does not work without a demonstration (i.e. a test data set where the problem can be reproduced consistently), does not help the development project to stay healthy, and definitely does not help keep its developers motivated. Just thinking aloud.